DV is a digital video format used world-wide for digital video cameras. The DV format is an international standard that was created by a consortium of companies typically referred to as the DV consortium. DV, originally known as DVC (Digital Video Cassette), uses a metal evaporate tape to record very high quality digital video. The DV video specification, IEC 61834, specifies the content, format and recording method of data blocks forming helical records on the digital tape. It also describes the common specifications for cassettes, modulation method, magnetization and basic system data, for digital video cassette recording systems using 6.35 mm (¼ inch) magnetic tape, and the electrical and mechanical characteristics of equipment which provides for the interchangeability of recorded cassettes.
DV video information is carried in a data stream at a rate of about 29 megabits per second (3.7 MByte/sec). A DV video frame typically includes 10 DIF sequences, each of which consists of 150 DIF blocks having 80 bytes of data each. In addition to video and audio data, each DV video frame includes extra data associated with the video and audio data called DV metadata.
DV metadata can include a wide range of data associated with the video data in a DV frame. For example, DV metadata can include the time and date that video was recorded, various settings on the camcorder at the time the video was recorded, and so on. According to IEC 61834-4, DV metadata is divided into 256 separate “packs”. Although 256 packs are reserved for DV metadata, many of the packs have yet to be defined. Each pack consists of 5 bytes. The first byte in each DV metadata pack is the pack ID, and the next four bytes consist of binary fields.
The DV format permits each DV video frame to stand on its own without having to rely on any data from preceding or following frames. For example, the same metadata is repeated numerous times within a DV frame. The redundancy built into each DV frame and the wealth of additional data (i.e., metadata) inherent to the DV format make DV video an ideal format for editing. However, various difficulties prevent current DV editing applications from taking full advantage of the unique features of DV video that make it ideally suited for editing.
In a typical DV scenario, video is recorded and converted to digital form in a camcorder. The video data on the digital tape can be played in a digital tape drive, such as the one in the camcorder, in a DVCR, or in a standalone unit. DV data can be transferred electronically via firewire to a computer's hard disk. The transfer process is typically performed by a capture driver, a standalone utility, or a component of an editing application executing on a computer such as a desktop personal computer. During the transfer process, the DV data is “wrapped” into a file format commonly understood by computers, such as AVI for Windows or Quicktime for the Mac. Therefore, once the transfer process is finished, the DV data on the computer hard drive is wrapped in a file format that standard editing applications can process. Various editing applications, such as Adobe® Premiere® Pro, enable nonlinear video editing through real-time video and audio editing tools.
However, as indicated above, current DV editing applications take little or no advantage of the rich information provided in the DV video format that makes it ideally suited for editing. The main reason for this is that it is difficult to extract the DV metadata from within DV video frames. DV metadata extraction currently requires an application developer to write its own custom code for extracting specifically desired metadata. In addition, an extraction process implemented by a DV editing application would be very processor intensive, which would hinder the performance of other editing functions of the application. One consequence of these difficulties is that DV metadata is generally not exploited by most DV editing applications.
Accordingly, a need exists for a way to extract DV metadata from DV data streams.